A pressure relief device is commonly used as a safety device in a system containing a pressurized fluid in gas or liquid form. For example, a pressure relief device may vent fluid from the system when the pressure in the system reaches a predetermined level—usually before it reaches an unsafe level. A number of emergency conditions, including fire and unintended chemical reactions, can create potentially dangerous pressure levels, which require immediate relief to preserve the safety of the system.
One type of pressure relief device is a rupture disk. Generally, a rupture disk has a flange that is sealed between a pair of support members, or safety heads, forming a pressure relief assembly. An example of a support member or safety head is disclosed in co-owned U.S. Pat. No. 4,751,938, the entire contents of which are incorporated herein by reference. The pressure relief assembly then may be clamped, or otherwise sealingly disposed, between an inlet pipe and an outlet pipe in the pressurized system. The inlet pipe may conduct pressurized fluid to an inlet side of the rupture disk. The outlet pipe may connect to an outlet side of the rupture disk, providing an outlet to a safety reservoir or to the environment. In another application, a rupture disk may be positioned on an outlet of a pressurized system without being sealed between an inlet and an outlet pipe—e.g., by welding, bolting, or otherwise attaching directly to the pressurized system's outlet.
One type of rupture disk may have a dome-shaped, rounded-shaped, conical shape, truncated conical shape, or other generally curved rupturable portion and can be either forward-acting or reverse-acting. A forward-acting rupture disk is positioned with the concave side of the rupturable portion exposed to the pressurized system, placing the disk under tension. Thus, when an over-pressure condition is reached—i.e., when the system pressure exceeds a safe or desirable level—the rupture disk may release pressure by bursting outward. Conversely, a reverse-acting rupture disk (also known as a reverse buckling rupture disk) is positioned with its convex side exposed to the pressurized system, placing the material of the disk under compression. Thus, when an over-pressure condition is reached, the rupture disk may buckle and tear open to vent pressurized fluid.
A further type of rupture disk comprises a generally flat rupturable portion that might be produced from metal, graphite, plastic or ceramic material.
A rupture disk industry has historically manufactured dome-shaped, rounded-shaped, or other generally curved rupture disks and/or flat rupture disks by moving rupture disk material from work station to work station for sequential processing steps, either manually, by an automated process, or by a combination of the two. Another method of manufacturing a rupture disk is disclosed in co-owned U.S. patent application Ser. No. 12/923,622 and co-owned PCT Application No. PCT/US10/50779, which published as WO2011/041456, the entire contents of each of which are hereby incorporated herein by reference.
Rupture disk assemblies using cutting structures are described in co-owned U.S. Pat. Nos. 4,236,648 and 5,082,133, the contents of which are hereby expressly incorporated by reference in their entirety. Exemplary stress concentration points are described in co-owned U.S. Pat. No. 5,934,308, the contents of which are hereby expressly incorporated by reference in their entirety.
The predetermined pressure differential at which a rupture disk will rupture is known as the “burst pressure.” The burst pressure for which a rupture disk is rated is known as the “nominal burst pressure.” The burst pressure may be set by way of the rupture disk's physical parameters, such as material thickness and dome height (also known as “crown height”). The burst pressure also may be set using various physical features, such as indentations. A rupture disk having an indentation—and methods of manufacturing such rupture disks—is disclosed, for example, in co-owned U.S. Pat. Nos. 6,178,983, 6,321,582, 6,446,653, and 6,494,074, the contents of which are hereby incorporated by reference in their entirety.
Physical features, such as score lines and shear lines (and other areas of weakness, also known as lines of weakness), may be used to facilitate opening of a rupture disk and control the opening pattern of a rupture disk. In a reverse buckling disk, for example, the disk will tear along a line of weakness when the disk is activated by pressure. A score or shear line may be used in combination with a stress concentration point or cutting member. Selected portions of the disk may be left unscored, acting as a hinge area, to prevent the disk from fragmenting upon bursting and the fragments from the disk escaping along with fluid from the pressurized system. A central portion of the disk that is partially torn away from the rest of the disk may be referred to as a “petal.”
A rupture disk may be combined with one or more elements to form a pressure relief device or a component of a pressure relief device. For example, a rupture disk may be combined with a holder device or a safety head assembly, to form a pressure relief device. A rupture disk may be fixed to a holder device by welding, crimping, adhesive bonding, compression fitting, or other suitable method.
Another type of a pressure relief device is a buckling pin valve. An example of a buckling pin valve appears in co-owned U.S. application Ser. No. 11/221,856, filed Sep. 9, 2005, and published as Publication No. US 2007/0056629, the entire contents of which are hereby incorporated by reference. Another example of a buckling pin valve appears in co-owned U.S. application Ser. No. 13/573,200, filed Aug. 30, 2012, the entire contents of which are hereby incorporated by reference. Components of a buckling pin valve may include a buckling pin, a spring, a collapsible washer, a Belleville spring, or other collapsible/deformable trigger element.
Another type of a pressure relief device is a vent. An example of an vent appears in co-owned U.S. application Ser. No. 10/831,494, filed Apr. 23, 2004, and published as Publication No. US 2005/0235584, the entire contents of which are hereby incorporated by reference. Another example of a vent appears in co-owned U.S. Pat. No. 7,950,408, the entire contents of which are hereby incorporated by reference.
A pressure relief device may be used with a sensor, such as a temperature sensor, pressure sensor, or an activation sensor.
The performance of a pressure relief device or a sensor may depend on a number of variables in its design. Variations in materials and manufacturing may result in any given two devices in a manufacturing lot of seemingly identical structure not activating at the same desired pressures. Similarly, variations in materials and manufacturing may result in any given two sensors from a manufacturing lot performing differently.
Currently, established codes and standards applicable to a pressure relief device focus on destructive testing as a means of qualifying a batch or lot of pressure relief devices. Typically, under routine testing practices, devices or components to be destructively tested are selected at random. For example, EN/ISO 4126-2 states that for a burst test, a “number of bursting disks . . . shall be selected at random from each batch and be subjected to burst testing . . . to verify that the burst pressure is in accordance with the specified requirements.” If the tested unit or units perform within expected standardized burst pressure limits (e.g., +/−5% for American Society of Mechanical Engineers (ASME) code applicable to rupture disks having a burst pressure of 40 pounds-per-square inch or above), then the entire lot of devices or components may be accepted. As a result, more is known about the units destroyed by the manufacturer than the (untested) units that ship to a user. It cannot be determined, for example, whether a destructively tested unit was a best, worst, or averagely performing unit relative to the rest of its batch or lot.
Further established quality checks for a rupture disk have focused on dome height and burst diameter. However, a more precise check of quality—down to a microscopic level—is desired.
Another concern for the performance of a pressure relief device or a sensor may be whether the device or sensor is a legitimate, authorized product, or whether it is a counterfeit product.
In light of the foregoing, it may be desirable to have a quality control system for a pressure relief device, or a related component such as a sensor, which may combine one or more of dimensional verification, individual part serialization, and image capture. It also may be desirable to provide a quality control system or method that utilizes non-destructive analysis and/or testing of a pressure relief device component. Using non-destructive methods may achieve increased confidence in the expected performance in a pressure relief device component, and/or reduce or eliminate the need for potentially costly and wasteful destructive testing. It may also be desirable to include a security feature to identify a pressure relief device, or a related component such as a sensor, as being a legitimate, authorized product. The system and method of the present disclosure provides one or more of these, or other, features.